In the past, testing of a gas discharge tube was performed using a hipot tester, a dielectric withstand tester, or a current-limited high voltage DC power supply. Prior art methods of testing gas discharge tubes for degradation over time tended to be expensive and often would result in the destruction of the gas discharge tube being tested. For example, traditional testing of gas discharge tubes that use clamping voltage and DC breakdown voltage from a surge protector test set can lead to arcing between the two electrodes of the gas discharge tube. A new, nondestructive method of testing gas discharge tubes is needed.